Water treatment equipment is broadly used in many industry fields. Traditional water treatment processes treat water by desalting source water. Typically, desalted equipment combines ion-exchange technology and electrodialysis technology. For example, Chinese Patent No. 96244875.4 shows an EDI device which combines ion-exchange technology and electrodialysis technology. In Chinese Patent No. 96244875.4, anion and cation resin is placed inside a dilute water chamber of the electrodialysis device and positive and negative electrodes are placed outside the device.
The advantages of this approach are that the same distance is achieved between every two arrays of membranes, the EDI device has a reliable and stable resistance, and the current intensity is relatively easy to control. The disadvantage of this approach is that it is difficult to fill the device with resins; special ion fiber knitting is necessary. To resolve this issue, an improved EDI module uses a spiral wound cylinder structure.
Chinese Patent No. 00220610.2 shows a multi-surface volume EDI module which consists of positive and negative electrodes, membrane bags and a frame. The anion and cation ion exchange membranes are combined with isolation net sheets to form membrane bags which fold to include concentrate water channels and dilute water channels. Each of the concentrate water channels and the dilute water channels connects to a different individual water collection chamber extending from a dilute/concentrate collection pipe. The dilute water channels are filled with ion-exchange resins, and consist of linked together rectangular channels.
It is known that the anode is set on the shell of this kind of EDI, while the cathode is placed within the shell. In other words, while the cathode is located within the EDI device, the anode is manufactured separate from the EDI device vessel and is attached to the outside of the device.
U.S. Pat. No. 6,190,528, issued Feb. 20, 2001 to Xiang Li et al. discloses a helical EDI apparatus having the disadvantages described above. The anode 10 of the EDI device disclosed in U.S. Pat. No. 6,180,528 is also manufactured separately and subsequently attached to the outside of the EDI device. U.S. Pat. No. 6,190,528 is incorporated herein by reference in its entirety.